Zilliox is cagey about his clients: "As a general rule, it suits me best not to comment on who I've worked for. Everybody is better off that way."

But when pressed, Zilliox says he focuses on local and state races in Virginia.

Opposition research for high-profile races for Congress or the White House is generally handled in-house, by the parties or by Washington's biggest law firms. In the 2012 presidential cycle a superPAC sprang up putting big money and a lot of manpower behind Democratic opposition research. GOP consultants are now pledging to do the same.

"An allied group dedicated to research to establish a private archive and public website that does nothing but post inappropriate Democrat utterances and act as a clearinghouse for information on Democrats would serve as an effective vehicle for affecting the public issue debate."

The Training

Zilliox alternates between sitting and standing at the front of the room, working his way through a day-long PowerPoint presentation. A small man with a large beard and a passion for digging into people's backgrounds, Zilliox is author of the Opposition Research Handbook, written in 1993, and now in its fourth edition.

"You're researching a candidate's background," he says. "But also not only his personal background and his business background but his political background and his political activities."

There are about 10 people in the room, each of whom paid $249 for a day of training. Among them are a handful of grizzled private investigators, who when asked if they've conducted opposition research before, say a lot of things like this, from Norman Williams: "I wouldn't say if I have or haven't."

Williams drove some 500 miles to Washington from Lexington, Ky., looking to expand his private investigation businesses further into politics. But also among the attendees are three young staffers from an environmental group, and a man from a public affairs firm who looks very uncomfortable when he sees my microphone.

Zilliox guides them through his basics of opposition research: Don't lie about what you're doing. Call it research, not an investigation. And don't do anything that you wouldn't want to explain on the 6 o'clock news.

"What you do affects your candidate, and the last thing you want to do is intimidate somebody," Zilliox counsels. "Lie to somebody, cause a scene in a courthouse. Do something that brings attention to yourself because, then it takes your candidate off message."

From Shoe Leather To Social Media

Opposition research relies on some old basics: court records, voting history and in some cases phone and financial records. And some new avenues made available by the Internet.

"If you're just looking for a drug store, you can [do a Google search] and take the first response. But when you're doing opposition research, if it gives you a couple hundred possible results, you've got to go through them all, because you never know what's going to be valuable when."

Case in point: the Mitt Romney 47-percent video. A short clip from this video was hiding in plain sight on YouTube, but it took a determined freelance opposition researcher to find it and get publicity.

Could the people in Zilliox's opposition research boot camp uncover the next politically explosive video? There's no telling. For Zilliox, some of his biggest blockbusters came in researching people thinking about a run for office. Candidates often run research on themselves to see what their opposition might find.

"I've researched people who almost everything they've said about their background wasn't true," he says. "They didn't have the resources they claimed, didn't work the jobs they had claimed. All sorts of stuff. I guess they just didn't think people would find out."

If it's out there, he says, someone will find it. These days there are lots of researchers looking.

Copyright 2013 NPR. To see more, visit http://www.npr.org/.

Transcript

AUDIE CORNISH, HOST:

It may only be April, but the recruiting and vetting process is already under way for candidates who will run for office in 2014. For many of them, that process includes hiring someone to do opposition research; first on the candidate, then on potential opponents.

NPR's Tamara Keith recently went to a training session billed as an opposition research boot camp.

TAMARA KEITH, BYLINE: Opposition research exists mostly in the political shadows. So perhaps it's fitting that this boot camp is in a generic conference room, in a generic airport hotel.

LARRY ZILLIOX: I want to thank you all for coming. My name is Larry Zilliox. I'm president of Investigative Research Specialists.

KEITH: Zilliox is a private investigator who specializes in opposition research. He's cagey about his clients.

ZILLIOX: I just, as a general rule, it suits me best not to comment on who we've worked for. Just - everybody's better off that way.

KEITH: But when pressed, he says he focuses on local and state races in Virginia. Opposition research for high-profile races for Congress or the White House, is generally handled in-house, by the parties, or by Washington's biggest law firms. In the 2012 presidential cycle, a superPAC sprung up putting big money - and a lot of manpower - behind Democratic oppo research. And now, Republican consultants are pledging to do the same.

Larry Zilliox is a small man with a large beard. He first wrote his Opposition Research Handbook in 1993. Now, he's on his fourth edition. He alternates between sitting and standing at the front of the room, working his way through a daylong PowerPoint presentation.

ZILLIOX: You're researching a candidate's background. But also not only his personal background and his business background, but his political background and his political activities.

KEITH: There are about 10 people in the room from vastly different backgrounds. There are a handful of grizzled private investigators who, when asked about their experience with this kind of work, say things like this...

NORMAN WILLIAMS: I wouldn't say if I have or haven't.

KEITH: Norman Williams drove in from Lexington, Ky., looking to expand his business further into politics. There are three young staffers from an environmental group, and a man from a public affairs firm who looks uncomfortable when he sees my microphone.

Zilliox guides them through his basics of opposition research. Don't lie about what you're doing. Call it research, not an investigation. And don't do anything that you wouldn't want to explain on the 6 o'clock news.

ZILLIOX: What you do affects your candidate. And the last thing you want to do is something that brings attention to yourself because then, it takes your candidate off message.

KEITH: There are the old basics - court records, voting history and in some cases, phone and financial records. But now, he says, it's all about the Internet and going beyond the top 10 results in your standard Google search.

ZILLIOX: If you're just looking for a drugstore, you can do that and take the first response. But when you're doing opposition research, if it gives you a couple hundred possible results, you've got to go through them all, because you never know what's going to be valuable when.

KEITH: Case in point - the Mitt Romney 47 percent video.

(SOUNDBITE OF RECORDED REMARKS)

MITT ROMNEY: All right, there are 47 percent who are with him, who are dependent upon government...

KEITH: A short clip from this video was hiding in plain sight on YouTube, but it took a determined freelance opposition researcher to find it and get it out. Could the people in Larry Zilliox's opposition research boot camp uncover the next politically explosive video? There's no telling. For Zilliox, some of his biggest blockbusters came in researching people thinking about a run for office.

ZILLIOX: I've researched people who almost everything they said about their background just wasn't true. They didn't have the resources they claimed. They didn't work in the jobs that they claimed - all sorts of stuff. I guess they just didn't think people would find out.

KEITH: If it's out there, he says, someone will find it. These days, there are lots of researchers looking.

Tamara Keith, NPR News.

(SOUNDBITE OF MUSIC)

ROBERT SIEGEL, HOST:

This is ALL THINGS CONSIDERED, from NPR News. Transcript provided by NPR, Copyright NPR.